Self-tightening drill chuck

ABSTRACT

A self-tightening drill chuck adapted to be mounted on a drill spindle for rotation about and reciprocation along the axis of the spindle has a guide body rotatable on the spindle about the axis and formed with a plurality of jaw guides inclined relative to the axis and spaced angularly thereabout and formations axially fixing the guide body on the spindle against substantial relative axial displacement. Respective jaws displaceable in the guides are formed with radially directed teeth meshing with a screwthread of an adjustment body fixed on the spindle against rotation thereon so that rotation of the adjustment body relative to the guide body in one direction displaces the jaws radially toward one another and opposite rotation displaces the jaws radially apart. Further formations secure the adjustment body on the spindle for limited relative axial displacement substantially greater than the relative axial displacement possible between the guide body and the spindle.

FIELD OF THE INVENTION

The present invention relates to self-tightening drill chuck. Moreparticularly this invention concerns such a chuck that is used on ahammer drill.

BACKGROUND OF THE INVENTION

A standard drill chuck has a guide body that may form the core of thechuck or that may be formed as a tightening sleeve and that is itselfformed with guides inclined to the chuck axis. Respective jaws areaxially slidable in these guides and have teeth that mesh with ascrewthread of an adjustment body that itself may either be the core ofthe chuck or a sleeve. Both these bodies are axially fixed on the drillspindle. The guide body is typically rotationally fixed on the drillspindle while the adjustment body is rotatable thereon so that relativerotation of these two bodies in one direction moves the jaws axiallyforward and radially inward toward one another and opposite relativerotation moves them axially back and radially apart. Thus it is possibleby rotation of this adjustment body to clamp a tool (or workpiece) inthe jaws and by opposite rotation to release this tool (or workpiece).

German patent document 3,727,147 whose U.S. equivalent is U.S. Pat. No.3,836,563 describes a system wherein the threaded adjustment body is thecore of the chuck and has a frustoconical surface formed with thescrewthread that serves to displace the jaws. The guide body is a sleevesurrounding the adjustment body and rotationally fixed on the spindle. Alocking ring is provided on the chuck and has teeth urged by a springinto axial engagement with teeth of the adjustment body to prevent itfrom loosening or from tightening excessively, as the screwthread is ofsuch a hand that the torque exerted via the jaws on the chuck partstightens the chuck. This locking ring is movable between a pair of endpositions defined by a pin set in a recess of the adjustment sleeve.

In German patent document 3,808,155 another arrangement is known whereinthe guide body is surrounded by an adjustment sleeve having an internalscrewthread and itself rotationally and axially fixed on the drillspindle. This arrangement also has a locking ring between the guide bodyand the adjustment sleeve for limiting tightening action.

Both systems use a one-piece drill spindle that cannot move axially orrotationally relative to the screwthreads. Thus this threaded bodyserves to transmit axial force, the hammering, to the jaws via thescrewthread on this body and the teeth on the jaws. The result is anextremely effective self-tightening action that in fact can lead to thechuck getting so tight that it becomes very difficult or even impossibleto loosen it and free the tool (or workpiece).

OBJECTS OF THE INVENTION

It is therefore an object of the present invention to provide animproved hammer-drill chuck.

Another object is the provision of such an improved hammer-drill chuckwhich overcomes the above-given disadvantages, that is which does notlead to the above-mentioned overtightening.

SUMMARY OF THE INVENTION

A self-tightening drill chuck adapted to be mounted on a drill spindlefor rotation about and reciprocation along the axis of the spindleaccording to this invention has a guide body rotatable on the spindleabout the axis and formed with a plurality of jaw guides inclinedrelative to the axis and spaced angularly thereabout and formationsaxially fixing the guide body on the spindle against substantialrelative axial displacement. Respective jaws displaceable in the guidesare formed with radially directed teeth meshing with a screwthread of anadjustment body fixed on the spindle against rotation thereon so thatrotation of the adjustment body relative to the guide body in onedirection displaces the jaws radially toward one another and oppositerotation displaces the jaws radially apart. Further formations securethe adjustment body on the spindle for limited relative axialdisplacement substantially greater than the relative axial displacementpossible between the guide body and the spindle.

Thus the adjustment body is more axially displaceable relative to thespindle than the guide body. As a result the axial forces will betransmitted along a path through the guide body, not through theadjustment body, to the jaws of the chuck. This will substantiallyeliminate the overtightening problem while not eliminating theself-tightening effect completely. The teeth will be spared thesubstantial load they are subjected to in prior-art systems so that thechuck of this invention will have a substantially improved service life.

According to another feature of this invention the formations fixing theguide body on the spindle include a pair of axially abutting surfacesone of which is on the guide body and the other of which is on thespindle. In fact the guide body is wholly axially nondisplaceable on thespindle.

In accordance with a further feature of the invention the spindleincludes a spindle sleeve forming the respective surface and carryingthe adjustment body. In addition the formations include an elementrotatably supporting the guide body on the adjustment body and axiallyspaced from the abutting surfaces. In this case the adjustment body iswithin the guide body.

The formations fixing the guide body on the spindle include a nonaxialpin engaged between the guide body and the spindle and an axiallyelongated notch through which the pin engages tangentially and in whichthe pin is engaged with axial but not radial or angular play. Thisarrangement ensures that the rotational coupling will be very strongwhile the axial decoupling remains effective. In addition the ends ofthe pin can serve as end stops for a standard locking ring.

It is also possible according to the invention for the guide body to bewithin the adjustment body. In this case the adjustment member is aninternally threaded sleeve surrounding the guide body. Furthermore inthis arrangement the spindle includes a spindle tube surrounding ahammer rod and the formations securing the adjustment body on thespindle are engaged with the spindle tube, not with the hammer rod.

DESCRIPTION OF THE DRAWING

The above and other objects, features, and advantages will become morereadily apparent from the following, it being understood that anyfeature described with reference to one embodiment of the invention canbe used where possible with any other embodiment and that referencenumerals or letters not specifically mentioned with reference to onefigure but identical to those of another refer to structure that isfunctionally if not structurally identical. In the accompanying drawing:

FIG. 1 is an axial section through a drill chuck according to thisinvention;

FIG. 2 is a section taken along line II--II of FIG. 1; and

FIGS. 3 and 4 are axial sections through two further chucks according tothis invention.

SPECIFIC DESCRIPTION

As seen in FIGS. 1 and 2 a chuck according to this invention is carriedon a drill spindle 1 centered on, rotatable about, and limitedly axiallyreciprocal along an axis 3. Fixed directly on the end of this spindle 1is a core body or sleeve 13 forming an axially forwardly directedannular shoulder 20 lying in a plane perpendicular to this axis 3.Carried in turn on this sleeve 13 is an adjustment body or sleeve 6formed centered on the axis 3 with a frustoconical screw thread 5.Rotatable on the adjustment sleeve 6 is a guide body or sleeve 4 formedcentered on the axis 3 with three identical and angularly equispacedguide slots 22 inclined at an acute angle to the axis 3. In addition thesleeve 4 has an axially backwardly directed abutment surface 16 bearingflatly on the surface 20 and an element 7 is provided to axially couplethe bodies 4 and 6 together. Each slot 22 receives a respective jaw 2having an inner edge formed with teeth 21 complementary to and meshingwith the screwthread 5.

The chuck is provided with a locking ring 8 that is limitedly angularlydisplaceable and axially displaceable against the force of a spring 9.When pushed forward by the spring 9 teeth 10 on the ring 8 engagecomplementary teeth 23 on the sleeve 4, so that in this interengagedposition rotation of the sleeve 4 is limited by the ring 8.

According to this invention the adjustment sleeve 6 is rotationallyfixed on the sleeve 13 by a tangential pin 14 that is fixed in thesleeve 6 but that engages in an outwardly open tangential notch 15formed in the sleeve 13. This notch 15 is axially extended so that thepin 14 and sleeve 6 can move axially somewhat relative to the spindle 1,unlike the sleeve 4 that is unable to make such axial movement relativeto the spindle 1. The ends of this pin 14 serve as indicated in FIG. 2to limit the angular movement of the ring 8 and therefore define thisring's end positions.

As a result of this construction the axial reciprocation or hammering inthe spindle 1 is transmitted to the jaws 2 primarily through the guidebody 4. The limited ability of the adjustment body 6 to move limitedlyangularly relative to this guide body 4 will avoid force transmissionfrom the adjustment body 6 to the jaws 2, thereby avoiding theovertightening that plagued the prior-art systems.

In FIG. 3 a system is shown having a guide body 4' that cannot moveaxially on the spindle 1 but that can rotate thereon. Balls 7'constitute formations axially but not rotationally coupling this body 4'with an adjustment sleeve 6' that is limitedly axially displaceable butrotatably nondisplaceable on the spindle 1. This coupling is hereeffected by a pin 11' extending diametrally through and fixed in thespindle 1 and having ends received in slots 12 formed in the body 6' .These slots 12 have a width measured perpendicular to the axis 3 that issubstantially the same as the diameter of the pin 11, but are axiallyelongated.

The arrangement of FIG. 4 has a spindle with an outer rotating sleeve 1'and an inner axially reciprocating hammer rod 1". The sleeve is coupledby balls 18 to an outer adjustment sleeve 6" like the sleeve 6'. Theseballs 18 fit in axially elongated slots 17 like the holes 12 but hereformed in the rotating spindle tube 1'. The hammer rod 1" beats on theabutment face 16 of the guide body 4".

I claim:
 1. A self-tightening drill chuck adapted to be mounted on adrill spindle for rotation about and reciprocation along the axis of thespindle, the chuck comprising:a guide body rotatable on the spindleabout the axis and formed with a plurality of jaw guides inclinedrelative to the axis and spaced angularly thereabout; means including aformation on the guide body and a formation on the spindle engaging theguide-body formation for fixing the guide body on the spindle againstaxial displacement on the spindle and for transferring axialdisplacement of the spindle directly to the guide body; respective jawsdisplaceable in the guides and formed with radially directed teeth; anadjustment body fixed on the spindle against rotation thereon and formedwith a screwthread meshing with the teeth of the jaws, rotation of theadjustment body relative to the guide body in one direction displacingthe jaws radially toward one another and opposite rotation displacingthe jaws radially apart; and means including interengaging formations onthe adjustment body and spindle securing the adjustment body on thespindle for limited relative axial displacement thereon.
 2. Theself-tightening drill chuck defined in claim 1 wherein the formationsfixing the guide body on the spindle include a pair of axially abuttingsurfaces one of which is on the guide body and the other of which is onthe spindle.
 3. The self-tightening drill chuck defined in claim 2wherein the spindle includes a spindle sleeve forming the respectivesurface and carrying the adjustment body.
 4. The self-tightening drillchuck defined in claim 2 wherein the formations securing the adjustmentbody on the spindle include an element rotatably supporting the guidebody on the adjustment body, the element being axially spaced from theabutting surfaces.
 5. The self-tightening drill chuck defined in claim 1wherein the adjustment body is within the guide body.
 6. Theself-tightening drill chuck defined in claim 1 wherein the formationsfixing the guide body on the spindle include a nonaxial pin engagedbetween the guide body and the spindle.
 7. The self-tightening drillchuck defined in claim 6 wherein the formations fixing the guide body onthe spindle include an axially elongated notch through which the pinengages tangentially and in which the pin is engaged with axial but notradial or angular play.
 8. The self-tightening drill chuck defined inclaim 6, further comprising a locking ring on the bodies angularlydisplaceable between end positions defined by ends of the pin.
 9. Theself-tightening drill chuck defined in claim 1 wherein the guide body iswithin the adjustment body.
 10. The self-tightening drill chuck definedin claim 9 wherein the spindle includes a spindle tube surrounding ahammer rod, the formations securing the adjustment body on the spindlebeing engaged with the spindle tube, not with the hammer rod.